It is known to apply a crosstalk cancellation technique, also referred to as “vectoring” to a group of telecommunication lines such as Digital Subscriber Lines (DSL). Vectoring is described in detail in the ITU-T Recommendation G.993.5. Vectoring allows for cancelling the crosstalk internal to a group of lines (vectoring group) or so called in-domain Far-End Crosstalk (FEXT), which is a major limitation to achieve high bitrates over lines that extend within a common cable or binder. Thus, vectoring increases significantly the available bit rate on such lines.
In order to limit the signal processing overhead caused by vectoring, typically a sub-group of a vectoring group is included in the crosstalk cancelling. That is, an arrangement for crosstalk cancelling according to the vectoring approach typically can cancel the crosstalk for a maximum number of disturbing lines of the vectoring group. As a consequence, there may be some lines in a vectoring group the crosstalk caused by which lines is not cancelled. Limiting the number of lines of the vectoring group that are included into crosstalk cancellation to a maximum number that is less than a total number of lines of the vectoring group is referred to as partial crosstalk cancellation. Partial crosstalk cancellation has less signal processing overhead than full crosstalk cancellation, which includes all lines of a vectoring group into crosstalk cancellation. Partial crosstalk cancellation is often applied for large vectoring groups which may be present in System Level Vectoring (SLV) covering many lines that are usually connected to multiple line cards of an access node.
It is known to define a number of spare positions within the maximum number of disturbing lines so that telecommunication lines that will join the vectoring group can initially be assigned to these spare positions. After a certain time, these spare positions will be freed again. Consequently, the number of disturbing lines the crosstalk of which is cancelled, is less than the supported maximum number. Typically, the number of spare positions can be configured by an operator of a DSL access network.